Fan



May 4, 1954 w. w. SPOONER FAN Filed Jan. 19,

2 Sheets-Sheet l 4/ I igmvrox. 7/" M 4/ W m fl/wdm I W W. W. SPOONER May 4, 1954 FAN 2 SheetsL-Sheet 2 Filed Jan. 19. 1951 INVENTOR. IQY/QO'DM/ Patented May 4, 1954 FAN William Wycliffe Spooner, Ilkley, England Application January 19, 1951, Serial No. 206,765

Claims priority, application Great Britain February 4, 1950 1 Claim. 1

The present invention relates to an improved fan for imparting motion to streams of air or gas.

According to the present invention an axial flow fan assembly comprises three concentric coplanar sets of annular blades for rotation with one another with or around a common shaft, the middle set of blades being disposed radially intermediate an inner annular set and an outer annular set and being inclined in the opposite direction to the inner and outer sets, the inner and outer sets being adapted to force a fluid in one axial direction and the middle set being adapted to force the fluid in the opposite axial direction.

The invention is further described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic sectional view of one form of construction of the improved fan or impeller in sectional side view, taken by way of example,

Fig. 2 is a fragmentary front elevation of the fan or impeller of Fig. 1.

The improved fan or impeller will be further described with reference to its application to a water heating boiler, or like heat interchanger.

In the arrangement shown in Fig. 1 an electric motor I drives a fan or impeller 2 located within a casing 3 and arranged adjacent a bank of finned tubes 4 extending between an upper header and a lower header. The fins of the tubes d are indicated at 5. The casing is provided with and covers 6, 'l of annular form.

As shown in Fig. 2, the impeller 2, mounted on a shaft 32, has three concentric substantially coplanar annular sets of blades 8, 9, Ill of which the inner and outer sets of blades 8 and H] are similarly inclined whilst the middle set of blades 9 are inclined oppositely to the inner and outer sets of blades 8 and I as shown diagrammatically by the lines l3, I9, 20 in Fig. 1. Thus the blades 9 will cause a gaseous medium to flow from right to left as viewed in Fig. 1 and as indicated by the arrow 29 whilst the blades 8 and it will cause the gaseous medium to flow in the opposite direction from left to right as indicated by the arrows 28 and 30.

Because the linear speed of the blades ill will be greater than that of the blades 9, the pitch of the blades E6 is less than that of the blades 9, and similarly the pitch of the blades 9 is less than that of the blades 8. Moreover, the pitch of the individual blades decreases outwardly.

Each individual blade is provided with a pair of flanges H, l2 and the blades are secured in position by riveting or Welding of the flanges respectively between hoops l3, M, l5 and boss it.

Each end cover 6, l is formed as a dished member with outer and inner annular recesses l7, 2!, 22, 23, respectively.

Outer and inner guide hoops 24, 25 are arranged between the impeller and the bank of finned tubes i in line with the hoops Hi, 15 of the impeller. It will thus be appreciated that with a gaseous heating medium within the casing 3 rotation of the impeller will cause circulation of the gaseous medium through the bank cuit will pass through the blades 9, around the finned tubes 4, around the annular chamber 23, around the tubes 4 through the blades 8 and around the annular chamber 2!.

The end cover 6 is provided with inlets 26 to permit the inflow of hot gaseous medium which is preferably controlled so as to maintain the temperature of the circulating gaseous medium within the casing at a more or less constant temperature. The hot gaseous medium may be products of combustion and in the application illustrated gas jets, as indicated at 21, are arranged at the mouths of the inlets 26 so that the products of combustion of the gas jets can be drawn into the casing through the inlets 26. The end cover 6 is provided with outlets 3! to enable the products of combustion to escape from the casing to compensate for the inflow through the inlets 26.

The finned tubes 4 extend between an inlet header 33 and an outlet header 34 provided with an inlet connection 35 and an. outlet connection 36 respectively.

Thus the present invention provides a relatively inexpensive water heater or steam raiser of light construction which cannot possibly be burnt out since the temperature of the products of combustion circulating in the casing is vastly less than the temperature of the gas jets 21. On the other hand, the high speed of flow of the gaseous medium and the re-circulation thereof in the circuits within the casing to afford a volume flow per minute which is large as compared with the rate of inflow of hot products of combustion and which is large as compared with the total volume of the gaseous medium contained in the casing, provides a rapid interchange of heat in spite of the relatively low temperature of the circulating gaseous medium.

I claim:

An axial flow fan assembly comprising a casing, a shaft rotatably mounted in said casing, means to rotate said shaft, three concentric substantially co-planar annular sets of axial flow blades on said shaft for rotation with one another and With said common shaft, said three sets of blades including an inner set, a middle set and an outer set, the middle set of blades being disposed radially intermediate said inner set and said outer set, all of said blades being inclined relative to a plane transverse of the shaft axis, the blades of said middle set being inclined in the opposite direction to the blades of said inner and outer sets, said casing having at least one cover member adjacent one side of said sets of blades, said cover member being of dished form and including an inner and an outer annular recess, said recesses joining approximately at the mid diameter of said middle set of blades, said inner and outer sets of blades being adapted to force a fluid in one axial direction and said middle set being adapted to force the fluid in the opposite axial direction, said recesses enabling said fluid to flow in two circuits in said casing, one of said circuits being through said middle set of blades in one direction and through said outer set of blades in the opposite direction, and the other of said circuits being through said middle set of blades in said one direction and through said inner set of blades in said opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 945,742 Boeckel et a1. Jan. 11, 1919 974,974 Kaiser Nov, 8, 1910 1,238,457 Thomson Aug. 28, 1917 1,261,457 Stott Apr. 2, 1918 1,349,482 Wood Aug. 10, 1920 1,991,194 Child Feb. 12, 1935 2,101,502 Keller es. 7, 1937 2,398,113 Parrish Apr. 9, 1946 2,407,223 Caldwell Sept. 10, 194.6 

